Cast molding is a known method for producing contact lenses. Generally, monomer mix is introduced into two mold parts which form the mold assembly. The monomer mix is then cured in the mold assembly to form a contact lens. The monomer mix is generally placed in an anterior, or female mold. The anterior mold has a concave surface that is used to shape the anterior surface of a lens. A posterior, or male mold is then brought into contact with the anterior mold so that the monomer mix is located in the cavity formed between the two molds. The posterior mold has a convex surface used to shape the posterior surface of the lens. The monomer mix is cured within the mold to form a contact lens. The anterior and posterior lens molds are then separated, and the cured lens is removed and placed into a package able to withstand the requirements for storage and shipping. The lens is usually packaged and shipped in the hydrated state so that, in addition to the lens, the package usually contains a storage solution.
Molds are typically discarded after the lens has been removed. While some of the mold materials may be recyclable, significant waste occurs and cost is added to the overall lens manufacturing process.
Recently, there has been interest in using molds, after the molding process is completed, as the lens package in which the finished lens is shipped and stored. U.S. Pat. No. 5,036,971 discloses the use of the anterior or female mold, as a packaging means for the molded lens. U.S. Pat. No. 5,143,660 discloses the use of the posterior or male mold as a packaging means for the molded lens. In both of these U.S. patents, the molding surface forms a part of the lens storage cavity. An advantage of these prior art approaches is that the lens can remain on the same surface from the time it is formed until it is removed from the package by the end user.
However, a problem with the approach disclosed in the patents is that the dimensions of such molding cavities may not be suitable for use as a storage chamber or final lens package for the lens. The cavity or chamber may have walls which are too steep to facilitate lens removal by the practitioner or patient. Further, the cavity in which the contact lens is molded and retained may have insufficient volume and therefore cannot hold a desired amount of lens solution thought to be required for storage and shipping.
In addition, in the case of hydrogel lenses, the lens is often hydrated after molding, but before shipping. During hydration, the lens swells. The dimensions of the anterior and posterior molding surfaces are generally smaller than the diameter of the hydrated lens. Therefore, the lens may not fit in the mold cavity in its hydrated state.